Television tube



April 1 K. SCHL'ESINGER 2,197,899

TELEVISION TUBE Original Filed Feb. 28, 1935 7/1 venfor:

Patented Apr. 23, 1940 s'r'rss GFFEQE Kurt Schlesinger, Berlin, Germany, assignor, by

mesne assignments, to Loewe Radio, Inc., a corporation of New York Original application February 28, 1935, Serial No. 1

8,660, now Patent No. 2,137,353, dated November 22, 1938. Divided and this application June 15, 1938, Serial N0. 213,731.

March 3, 1934 In Germany The present invention relates to cathode ray tubes for television and the like and more particularly to tubes in which the ray is focussed on the screen by means of an electrostatic lens and, afterwards, is deflected by means of one or tWo pairs of plates furnished with deflecting voltages.

The present application is a division of application Serial No. 8,660, filed February 28, 1935, Patent No. 2,137,353, dated November 22, 1938.

It is an object of the invention to impart to one or both pairs of deflecting plates a common bias. It is a farther object of the invention to impart to one or both pairs of deflecting plates a common bias varying with the deflection.

The invention is illustrated in the accompanying drawing which is a diagram of the head of a cathode ray tube and the elements connected with its electrodes.

In the drawing, l is the cathode having anemissive spot of say .3 mm. diameter, ii is a diaphragm, having a smaller aperture 1 which is to be reproduced on the luminous screen, 9 is a tubular member, l2 the anode, I 3-44 the first and i5-l6 the second pair of deflecting plates. The anode i2, the diaphragm i3, and also a conductive wall coating ll! of the tube (the glass Wall is not shown) are earthed whilst the cathode has a high negative potential and 9 a mean one tapped at the anode battery 48.

Each pair of deflecting plates-as already said previously-are operated in push-pull. This method of operation is illustrated diagrammatically by a. tap to the middle of the secondary winding of each of two transformers 36 and 3?, the primary windings of which are fed by relaxation oscillation generators I? and i8 the two middle tappings in question being earthed dynamically via condensers 38 and 39. The centres of the transformers 36 and 31 are provided With negative biasses compared with the anode. These biasses are derived for example through the medium of a potentiometer 4| from the battery 10.

Each deflecting condenser 13-! and l5-l5 upon application of the negative bias according to the invention acts against the surroundings (I2, I9) raised to anode potential as a concentration electrode which concentrates the ray, however, only in the direction of its electrical field, and does not afiect the same in the direction of the plane of the plates. If the bias iii according to the invention were not provided, the plates act in optical dispersing fashion on the ray, as apparently a small difierence in potential exists between their potential and the electrons of the ray.

By application of the negative bias according to the invention this disturbing deconcentrating effect disappears, and upon additional increase of the bias may even be changed to its contrary viz. a concentrating efiect. In many cases it is 5 possible to use in place of two different biasses for the deflecting condensers i3-i4 and lE-l'o' the same bias, or even to connect the one, viz. I5l6, with the anode directly to bias merely l,0 l3i4.

It is even possible with the circuit arrangement as described to obtain a smaller image point than would be possible without this measure. The applicant believes that owing to the negative biassing of the deflecting condensers the position of the resulting refractive plane is approached more and more toward the luminous screen, by which assumption this effect would be quite readily explicable.

An additional advantage of the measure according to the invention is the minimizing of the transverse currents of the ray flowing to the plates, and accordingly a closer approximation towards an entirely powerless deflection.

In addition to a constant bias it is also possible to introduce an alternating voltage of the same frequency as the deflecting voltage or the double of it between the centres of the transformers and earth. By means thereof it is possible to compensate electrically errors in the picture at the edge thereof caused by incomplete compensation of the marginal fields of the plates. Lack of sharpness at the edge of the picture, for example, may be wholly overcome by an alternating voltage of twice the frequency of the deflecting voltage and suitably adjusted amplitude. The means for obtaining such voltage are well known in the art.

The biasses employed in accordance with the invention depend on the arrangement of the deflecting plates in relation to the anode, the wall coating and in relation to each other, but in each individual case may be determined in simple fashion by experiment. As regards their extent, the biasses employed are of the order of about 10% of the anode potential.

It may specifically be remarked that the attempt made in the above to explain the phenomena is not sufllcient to provide a complete explanation in all cases. The one certain fact is that the deflecting plates exert an optically deforming efiect on the ray, which may be fully compensated in the manner according to the invention by the use of biasses, which difier in different cases as regards their extent and possibly also their sign. The arrangement for reverse phase operation of the deflecting plates has been quoted merely as an example. Naturally all otherknown, arrangement may be employed for this purpose.

The method according to the invention may be employed fundamentally in connection withall Braun tubes having an electron-optical system,

preferably, however, with high-vacuum tubes and more particularly those according to. the drawing.

I claim:

1. In combination a cathode ray tube including electrodes forming a cathode ray'defiecting condenser and at least one further electrode mounted near the first said: electrodes and bein at least partly plate-shaped and disposed in a cross-section of said cathode ray tube, means for supplying said deflecting condenser with reverse phase deflecting voltages, means for applying to said further electrode a fixed potential, and means for applying to the electrodes of saiddefleeting condenser, taken as a Whole, a common variable bias relatively to said further electrode, the frequencyof said bias being equal to that of the mentioned deflecting voltages.

2. In combination a cathode ray tube including electrodes forming a cathode ray'defiecting condenser and at least one further electrode mountednear the first said electrodes and being at least partly plate-shaped and disposed in a cross-section of said cathode ray tube, means for supplying said deflecting condenser with reverse phase deflecting voltages, means for applying to said further electrode a fixed potential, and means for applying to the electrodes of said deflecting condenser taken as a Whole, a common variable. bias relatively to said further electrode, the frequency of said bias being twice as high as that of the mentioned deflecting voltages.

3. In combination a cathode ray tube including electrodes forming a cathode ray deflecting condenser and at least one further electrode mountednear the first said electrodes and being at least. partly plate-shaped and disposed in a cross-section of said cathode ray tube, means for supplying said deflecting condenser with reverse phasedefiecting voltages, means for applying to said 'further electrode a fixed potential. and ,meansforapplying to the electrodes of said deflectingcondenser, taken as a whole, a common constant and a common additional variable bias relatively to said further electrode.

4. In combination a cathode ray tube including electrodes forming a cathode ray deflecting condenser and at least. one further electrode mounted near the first said electrodes and being at least partly plate-shaped and disposed in a cross-section of said cathode ray tube, means for supplying said deflecting condenser with reverse phase deflecting. voltages, means for applying to said further electrode a fixed potential, and means for applying to the electrodes of said deflecting condensentaken as a whole, a common alternating bias relatively tosaid further electrode.

KURT SCHLESINGER. 

